Production of L-phenylacetylcarbinol (L-PAC) by encapsulatedSaccharomyces cerevisiae cells

In the present study, benzaldehyde was converted by both the free cellsSaccharomyces cerevisiae (ATCC 834) and those immobilized in the calcium alginate liquid-core capsule intoL-PAC during anaerobic fermentation in a medium containing benzaldehyde. In a free cells survey, skipping aerobic adaptation before anaerobic fermentation caused all of benzaldehyde to be converted by 220 g (wet weight) of cells in 100 mL of the medium even at a higher concentration of 8 g/L benzaldehyde. The yield of L-PAC based on the moles of converted benzaldehyde increased as the amount of benzaldehyde dose was increased. The encapsulation protected cells effectively from the toxicity of benzaldehyde. Even a small quantity, 1.1 g (dry weight), of encapsulated cells in 100 mL of the medium containing 0.6% benzaldehyde converted more than 95% of the benzaldehyde, and the corresponding yield of L-PAC was about 40%. The production of L-PAC by the encapsulated cells depended on the pH of the medium. The conversion of benzaldehyde decreased slightly, but yield of L-PAC increased as the pH of the broth solution was fixed at a lower value. Biotransformation in a small side reactor of the batch system caused higher yield of L-PAC than that in the batch reactor containing the same quantity of encapsulated cells during the first 4 hours of fermentation.